High temperature, solid oxide electrolyte fuel cell configurations are well known in the art, and are taught in U.S. Pat. No. 4,395,468 (Isenberg). The air electrode of the fuel cell can be comprised of doped or undoped oxides or mixtures of oxides in the Perovskite family, such as LaMnO.sub.3, CaMnO.sub.3, LaNiO.sub.3, LaCoO.sub.3, LaCrO.sub.3, and the like. Self supporting air electrodes are taught in U.S. Pat. No. 4,751,152 (Zymboly). The usual air electrode material is LaMnO.sub.3 doped with Ca or Sr, as a substitute for part of the La. In all cases, the air electrode must be porous, that is, have from 20% to 40% porosity (60% to 80% of theoretical density) in order to be operable in the fuel cell.
U.S. Pat. No. 4,562,124 (Ruka) taught that one difficulty in constructing fuel cells using modified lanthanum manganite air electrodes was, that when the air electrode was modified to have the highest electrical conductivity, it would have a higher coefficient of thermal expansion than some other materials typically used in making the fuel cell, such as those used in the stabilized zirconia electrolyte or the stabilized zirconia support tube. This patent taught a sintered, single phase, solid solution of a compound having the formula: EQU La.sub.1-X-.omega. (M.sub.L).sub.X (Ce).sub..omega. (M.sub.S).sub.1-y (M).sub.y O.sub.3,
where M.sub.L =Ca, Sr or Ba; M.sub.S =Mn or Cr; and M=Ni, Fe, Co, Ti, Al, In, Sn, Mg, Y, Nb or Ta and where .omega. is from about 0.05 to about 0.25, preferably 0.1 to 0.2; and y could be 0. Here, the oxide, carbonates or oxalates of all the metal components including Ce were homogeneously mixed and then sintered, to get the Perovskite-like crystal structure. Preferred compounds were La.sub.0.3 Ca.sub.0.5 Ce.sub.0.2 MnO.sub.3 and La.sub.0.3 Ca.sub.0.5 Ce.sub.0.2 CrO.sub.3.
It has subsequently been found that the amount of porosity in air electrode tubes made of La-Perovskite based air electrode materials may be difficult to control, where in many cases porosity drops to 10% to 15% due to uncontrolled sintering. What is needed is an air electrode made from a powder composition which will not only satisfy thermal coefficient matching problems, but also solve porosity control problems. It is one of the main objects of this invention to provide such powders.